Legal action is being taken by some frontline ambulance staff unhappy at shift changes introduced by Great Western Ambulance Service.

The changes were introduced in November across Wiltshire, Gloucestershire and Avon to improve response times.

However, staff have complained that the new shifts are unsociable, cause fatigue and affect their work-life balance.

The Association of Professional Ambulance Personnel (APAP) is supporting members who work for GWAS in taking their grievances to an industrial tribunal and Unison has had about 20 members of staff lodging industrial tribunal issues with it.

APAP members are alleging breach of contract as they say GWAS imposed substantially different rota systems without agreement and indirect sex discrimination as it puts female members of staff at a disadvantage regarding child care and personal security.

Jonathan Fox, spokesman for APAP, said: “It is unusual for such action to be taken and it reflects the frustration and desperation that staff feel.”

Unison called off industrial action in February but officials continue to meet with GWAS management to thrash out concerns about the shift patterns.

Chris Hewett, Unison steward and a paramedic supervisor in Bristol, said: “We hope the talks with management will bring successful resolution and modifications to the rosters. The issue is do you want to be treated by a miserable, tired paramedic or one who is top of their game?”

A spokesman for GWAS said he was aware of 27 members of staff seeking to bring tribunal cases out of almost 1,000 staff.